Charging problem

[mercoupe50]

I have a 1966 Superformance Cobra with a 460 Ford SVO engine and has a voltage regulator that is separate from the alternator.
My amp meter jumps around pos to neg and back. The lights do fluctuate so the voltage is actually fluctuating.

This occurs when:
The battery is fully charged and with no electrical load on the system ie, lights, heater blower, radiator fans etc. and is at fast idle or on the road.

It stops or fluctuates far less if:
The battery is not fully charged and is showing it is chaging on the amp meter.
A load is on the system ie, lights, blower motor, radiator fans.
The engine is at idle.

I have changed the alternator and regulator.

The belt is tight and not slipping.

I have checked the battery ground to frame, engine block ground to frame, aternator and regulator groind to engine block.

I have had this problem for a few years but I don't drive the car much so it wasn't that important. I would like to see it so now it has been elevated in importance.

Your comments will be appreciated.

[Blas]

Drop a message offline and I'll send give you my phone number. I have a couple things that may solve the issue. Pretty common.

[347stroker]

Mercoupe get one of Blas's wiring diagrams if you don't already have one. The odds are in favor of a fried ammeter. Pull it and replace it with a volt meter. The ammeter is part of the charging circuit so if it is bad then you get erratic charging. Just my opinion as Blas will probably chime in with a definitive answer.
Tom